Our aim is to investigate the effect of a diet low in total calories from fat (15-20%), on the coronary heart disease (CHD) risk factors of a cohort of 200 healthy women age 45-69, and to compare them to age-matched women who will be consuming the usual American diet (higher than 35% total calories from fat). The overall objectives are: 1) to better understand the evolution of CHD risk factors after menopause, the period when a sudden escalation of risk and an increase in CHD in women occurs, and 2) to determine whether a low fat diet has a potential to lower or prevent the increase in CHD risk factors which otherwise occurs at this age in women. The study subjects are participants in a Nutrition Clinical Unit (NCU) which is a part of the "Women's Health Trial," a controlled clinical trial to attempt to lower the risk of breast cancer with a low-fat diet. The candidate is one of two Principal Investigators of this NCU currently planning to devote 15% of her time to the NCI study. The NCI study focuses primarily on cancer end-points and also monitors serum cholesterol and adherence to the dietary intervention. If the RCDA is funded, then in addition to data collected under the NCI protocol, the known CHD risk factors, including serum lipid profiles, blood pressure and Type A behavior, will be collected by the applicant at the baseline, 4 and 8 weeks after the start of the dietary intervention and every 4 months thereafter. This will provide an excellent cost effective mechanism to study the effect of a low-fat diet on CHD risk factors in women at a critical age (45-69) when a sharp increase in CHD risk and incidence occurs, and importantly, will enhance the candidate's expertise by allowing her to gain the necessary skills of conducting all phases of a CHD risk reduction clinical trial.